In recent years, there is a need to reduce a leak amount in a seal ring used for various hydraulic devices (particularly, an automatic transmission for a car) for the purpose of improvement in controllability and performance of the devices.
As a measure to reduce a leak amount, a demand for a seal ring made of a resin such as PEEK or PPS manufactured by injection molding, in which the shape of a cut provided in a place in the circumference of the seal ring is set as a special step cut is increasing.
On the other hand, in the interest of reduction in weight of a device on the other side, miniaturization, and VA (value analysis), use of a material which is not desirable as a sliding member such as aluminum or rolled soft steel is increasing. In the case of using such a material for a sliding member in a seal ring, it is concerned that the seal ring slides in a state where a foreign matter enters an outer peripheral face of the seal ring, and metal on the other side wears.
Literature disclosing conventional techniques related to the present invention are, for example, Patent Literature 1 and 2.